DE102014118654A1 - Thermoplastic container and method of manufacturing the container - Google Patents

Abstract

The invention relates to a container (1) made of thermoplastic material with at least one inner reinforcing rib (3) in a container wall, wherein the reinforcing rib (3) is formed by at least one line-shaped groove track (4) in a container outer wall (2a), the groove track (4 ) extends over a length on the container outer wall (2a), the groove track (4) is formed by a plurality of recesses (5) in the container outer wall (2a) spaced apart from each other and between the recesses (5) respectively Material bridges (6) are provided, each having a smaller depth than the recesses (5). The invention further relates to a method for producing such a container (1) by extrusion blow molding or deep drawing.

Description

The invention relates to a container made of thermoplastic material with at least one inner reinforcing rib in a container wall.

The invention further relates to a method for producing such a container.

In principle, it is known to provide containers made of thermoplastic material with reinforcing ribs, which increase the flexural rigidity and the compressive strength of the container walls. In the case of bottles, for example, it is known to provide these with circumferential reinforcing ribs. In injection molded containers it is known to mold reinforcing ribs to the container walls. Such reinforcing ribs may be formed so that they protrude into the container volume and consequently also at the expense of the container volume. Alternatively, reinforcing ribs may be provided on the outside of the container walls, which could hinder depending on the purpose of the container. For injection molded plastic containers, additional reinforcing ribs or other reinforcing geometries will accumulate material in the container wall which may lead to sink marks on the container. These sink marks are caused by a slower cooling of the material after the completion of the container in the thick areas of the container and are often not visually desirable. In addition, such accumulations of material go hand in hand with increased consumption of plastic material and significantly increase the container weight.

To limit the deformation of containers today oblique stiffening grooves (wedges) are introduced into the container wall, which protrude from a stiff area on the side wall in the deforming surface. The effect and the applicability are limited and the associated volume loss of useful volume is large.

For sheet metal containers, it is generally known to provide in the container walls rectilinearly extending beads, which optionally intersect. However, such stabilization measures can not be transferred, for example, to the production of extrusion blow-molded hollow bodies made of thermoplastic material. In extrusion blow molded containers made of thermoplastic plastic corrugations act like a bellows, which increases the deformability of the container under pressure.

The invention is therefore based on the object to provide a container made of thermoplastic material, which is provided with at least one reinforcing rib, which causes an effective reinforcement of the container with the lowest possible volume loss and the least possible use of material.

The invention is further based on the object of providing a suitable method for producing such a container.

The container according to the invention should also be designed as a large-volume container, which has reinforced large-area walls. Such containers are, for example, fuel tanks, oil tanks, mop water tanks or additive tanks that can be obtained by extrusion blow molding.

The container according to the invention should in particular be weight-optimized.

The object is achieved with the features of claim 1 and with the features of the independent method claim. Advantageous embodiments of the invention will become apparent from the dependent claims.

According to one aspect of the invention, a container of thermoplastic material is provided with at least one internal reinforcing rib in a container wall, wherein the reinforcing rib is formed by at least one line-shaped groove track in a container outer wall, the groove track extends over a length on the container outer wall, the groove track through a Is formed plurality of wells in the container outer wall, which are spaced from each other and wherein between the wells each material bridges are provided, each having a smaller depth than the wells. Internal reinforcing rib according to the invention means that the reinforcing rib protrudes into the volume of the container.

The container according to the invention may be a large-volume container having at least two in comparison to the other container walls large-area container walls, which may be arranged, for example, opposite each other. In at least one of the large-area container walls, at least one reinforcing rib, preferably a plurality, is provided. The reinforcing rib extends linearly or is formed as a linear groove track.

A groove track in the sense of the present application is a track of a plurality of line-shaped spaced groove sections or depressions in the container outer wall. The groove track can basically extend straight, alternatively, the groove track be arranged in an arc. The groove track is formed according to the invention by a plurality of linearly spaced recesses or groove portions in the container outer wall.

In principle, it is possible to provide the groove track through a plurality of depressions in the container inner wall, but the arrangement of the groove track in the container outer wall is preferred, so that the resulting reinforcing rib is at the expense of the container volume.

The material bridges of the container wall formed in each case between the depressions have a smaller depth than the depression, wherein the material bridge can in principle be aligned with a surface of the container outer wall outside the groove track. In principle, however, is also within the scope of the invention that the material bridge in turn are formed as depressions of the container outer wall, which, however, then have a smaller depth than the wells.

The solution according to the invention has the advantage that a container designed in this way can be produced by extrusion blow molding, in particular because the depressions are provided in the container outer wall. Compared to a continuous groove has a groove track with a plurality of mutually spaced wells and provided between the wells material bridges the advantage that this groove track does not weaken the container wall in the sense of a notch or in the sense of a bead and thus actually in a container made of thermoplastic material contributes to a significant stabilization of the container wall. The fact that the groove track is not formed as a continuous rib, but rather is interrupted by material bridges, also results in the advantage that the reduction of the useful volume of the container compared to a continuous reinforcing rib inside the container keeps within reasonable limits. The width of the recesses may be relatively small in relation to the length of the recesses.

In a preferred variant of the container according to the invention it is provided that the plastic of the container wall is accumulated in the region of the material bridges, so that the wall thickness of the container wall in the region of the material bridges is greater than in the region of the depressions.

Particularly preferably, the wall thickness of the container wall in the region of the material bridges is stronger than the wall thickness of the container wall outside the groove track, so that the material bridges each form thickenings of the container wall, which ultimately lead to a significant stabilization of the container wall in these areas. Such thickening can go at the expense of the wall thickness of the container wall in the region of the wells, where a thinner wall thickness is much less critical because of the smaller wall surfaces, so that the total production of the container according to the invention hardly requires increased material costs. The container weight can therefore correspond to the container weight of a container without reinforcing ribs with largely the same average wall thickness.

Particularly preferably, the recesses have a length and a width, wherein it is provided that the length is 4 to 7 times the width of the recesses. For example, the material bridges may have a length that is 0.3 times to 0.5 times the length of the wells.

Length means in this context an extension in the direction of the groove track, width means an extension transverse to it.

Appropriately, the wells are arranged at regular and equal distances from each other.

The material bridges may have a length that is less than or equal to twice the wall thickness of the container outside the groove track.

In the container wall a plurality of reinforcing ribs, preferably in the form of a plurality of rectilinearly extending groove tracks may be provided, which preferably intersect. The groove tracks may be formed, for example, X, T or S shaped. These reinforce the container wall transversely to its areal extent.

A further aspect of the invention relates to a method for producing a container having one or more of the features described above, wherein the method is characterized in that the container is obtained by extrusion blow molding or deep drawing of at least one preform made of thermoplastic material, the method providing or the extrusion of the preform, the introduction of the plasticized preform into a tool and the forming and shaping of the preform within the tool, wherein at least one reinforcing rib in the form of a linear groove track in the formation of the container within the closed tool by means of at least one tool insert or a Tool slide is produced, which is designed as a rib-shaped strip which protrudes into a cavity of the tool, wherein the strip has a plurality of grooves and webs and wherein the webs recesses in the Produce container outer wall and in the webs plasticized plastic is accumulated.

For the purposes of the present invention, a preform may be a tubular preform which is shaped in the first heat of the extruded plastic, that is to say by utilizing the plastication heat of the plastic within a multi-part blow molding tool. However, the method may include extrusion blow molding in the sense of a twin sheet blow molding process in which either two sheet-like, plasticized preforms are extruded and remoulded in a multi-part blow mold. Such a method may also include providing a tubular preform which is longitudinally split on opposite sides and whose parts are laid into sheet-like preforms.

A blow-molding tool in the sense of the present invention preferably comprises two or more blow-molded parts which each have cavities and which are movable relative to one another on a so-called closing frame and can be brought into contact with one another. When the blow molding tool is closed, the cavities of the parts of the blow molding tool form a mold cavity whose boundary contour substantially corresponds to the outer contour of the container to be manufactured.

The reforming and shaping of the preform or preforms is carried out either by gas pressure of the mold cavity or by evacuation of the mold cavity or by gas pressure of the mold cavity and evacuation of the mold cavity. The tool insert (fixed) or the tool slide (retractable into and out of the cavity) is expediently designed as a comb-like strip with grooves and intermediate webs.

As a tool in the context of the invention, a thermoforming tool may be provided, in which case the method comprises heating and plasticizing two semi-finished thermoplastic material as preforms and the semi-finished each in a tool and are formed and then joined to the container ,

Conveniently, the grooves have a length, a width and a depth. The length of the grooves may correspond approximately to the length of the material bridges and the length of the grooves is expediently dimensioned so that the wall thickness of the molded container in the region of the material bridges is greater than the wall thickness of the container in the region of the depression, preferably greater than outside the groove track.

Length means in this context an extension in the direction of the extension of the bar, width, however, means an extension across it.

In this way, steep-walled reinforcing ribs can be introduced from the outside into the container, for example via rigid "swords" as a tool insert or tool slide in the blow mold or in a deep-drawing tool, which are ideally demoulded in the direction of the tool opening. The tool insert or the tool slide can be designed as a comb-like or rib-shaped strip, which causes, for example, melt to pass from both sides of a forming bead during the blow molding process and the materials of the preform or of the subsequent container wall can connect to one another from both sides. The length of the grooves is ideally dimensioned so that the plasticized material of the preform can not completely penetrate into the groove base, but rather forms a fold of the preform, in which the container wall is "double-layered" and so between the webs material bridges or material thickening arise. The thus accumulated plastic forms material bridges, which cause a stiffening of the groove track. Preferably, the length of the grooves is designed so that, as already mentioned above, the preform is not completely immersed in the profile of the rib-shaped strip and connects to each other on both sides of the webs.

The penetration of the plastic into the grooves or into the profile of the strip can basically be made more difficult by the fact that a metal wire or a plastic cord is placed over the strip, which penetrates into the plastic of the preform in the production of the container and is lost in the latter ,

In a preferred variant of the method according to the invention, it is provided that the length of the grooves is between 1.8 times and four times the wall thickness of the preform. During the formation of the groove track, the plasticized material flowing around the strip is stretched in the region of the later depressions and compressed in the area of the later material bridges.

The invention will be explained below with reference to an embodiment shown in the drawings.

Show it:

1 FIG. 2: a perspective view of a container according to the invention, which is designed as a fuel tank, FIG.

2 FIG. 2 is a schematic representation of a portion of an open blow molding tool. FIG.

3 a perspective view of a reinforcing rib inside the container,

4 FIG. 2: a plan view of the cavity of a blow molding tool, FIG.

5 a side view of a tool insert for producing the reinforcing rib and

6 : An end view of the tool insert in the blow mold.

1 shows a container ( 1 ) according to the invention, which is designed for example as a fuel tank for a motor vehicle. The container 1 is made of thermoplastic material and was produced by extrusion blow molding of a preferably multi-layer extrudate based on polyethylene. The invention is basically to be understood that the container 1 may also have been prepared as a so-called monolayer container based on a single-layer extrudate of thermoplastic material. The container 1 includes a container wall 2 which encloses a filling volume. In the in 1 illustrated embodiment, the container 1 formed as a so-called saddle tank with two chambers communicating with each other, however, the invention should be understood to mean that the container 1 can have any shape. The container 1 may for example have been formed as a simple cuboid or cube-shaped structure.

The container wall 2 of the container 1 can have relatively large wall areas, with protruding into the container volume reinforcing ribs 3 are provided.

In the example according to 1 become the reinforcing ribs 3 by substantially linearly extending groove tracks 4 in the container outer wall 2a educated. The groove tracks 4 are each formed linear and extending straight, each with two groove tracks 4 to cross each other at about right angles.

The groove tracks 4 are through a variety of wells 5 in the container outer wall 2a formed, which are spaced apart, wherein between the recesses 5 each material bridges 6 are provided, each having a smaller depth than the wells 5 ,

The wells 5 were used in the manufacture of the container 1 by impressions of the container outer wall 2a generated.

3 shows the formation of a reinforcing rib 3 on a container inner wall 2 B at which each well 5 in the container outer wall 2a a corresponding projection 7 generated.

The following is based on the 2 to 6 the manufacturing process of the container 1 explained according to the invention.

2 shows purely schematically an open Blasformhälfte 8th an incompletely illustrated blow molding tool and one with respect to the blow mold half 8th placed preform 9 made of thermoplastic material. The container 1 For example, by conventional extrusion blow molding a tubular preform 9 have been prepared, wherein the preform 9 can be extruded one or more layers by means of an extrusion head arranged above the blow molding tool. The blow molding tool can, for example, two blow mold halves 8th comprise, which can perform an opening and closing movement on a closing frame, not shown. The term blow mold half 8th comprises a conventional platen and a tool part arranged on the platen 10 which is a cavity 11 having a part of the outer contour of the container to be manufactured 1 Are defined.

The cavities 11 two blow mold halves 8th For example, they may form a closed mold cavity, the contour of the mold cavity being the shape of the complete container to be manufactured 1 equivalent.

As already mentioned, the blow molding tool can have more than two tool parts 10 include, the manufacturing method may for example be designed as a so-called twin-sheet blow molding process, in which web-shaped preforms are formed in a three-part blow mold.

Inside the cavity 11 of the tool part 10 For example, a tool insert is provided as a rib-shaped bar 12 is trained. The bar 12 includes a variety of grooves 13 and footbridges 14 , where the webs 14 the wells 5 in the container outer wall 2a generate and in the grooves 13 the material bridges 6 be formed.

The method first involves providing or extruding the preform 9 , Moving the preform between the open blow mold halves 8th of the blow molding tool or the extrusion of the preform 9 in the direction of gravity between the open blow mold halves 8th , The blow mold halves 8th become the preform 9 closed, within the through the cavities 11 Formnestes formed is the preform 9 expands and thereby deformed and against the walls of the cavities 11 formed. This is where the preform lies 9 against the trained as a tool insert rib-shaped bar 12 and creates a reinforcing rib 3 the in 3 shown type. The rib-shaped bar 12 has a thickness and a length, with the bar 12 lengthwise of the grooves 13 is broken and the between the grooves 13 arranged webs 14 have a length dimensioned such that the preform 9 in the formation within the blow mold or during its expansion, for example by means of blowing air, not completely into the grooves 13 the bar 12 dives in and on both sides of a footbridge 14 connects together so that in the container wall 2 material bridges 6 be formed in the form of thick places.

As in particular from the synopsis of 5 and 6 it can be seen, the one bar 12 According to the invention, the thickness of the strip is 12 about only a quarter of the length of the grooves 13 so that the preform while flowing around the bar 12 during its formation not only of two in the longitudinal direction of the bar 12 opposite sides of a bridge 14 but also a connection of the preform in the direction of the thickness of the bar 12 , so across, is achieved.

4 illustrates a view into an opened tool part 10 with one in the cavity 11 of the tool part 10 arranged strip 12 ,

The contour of the tool part 10 according to 4 to be manufactured container 1 does not match the contour of the in 1 illustrated container 1 ,

LIST OF REFERENCE NUMBERS

1

container

2

container wall

2a

Vessel wall

2 B

Container inner wall

3

reinforcing ribs

4

groove tracks

5

wells

6

material bridges

7

head Start

8th

blow mold halves

9

preform

10

tool part

11

cavity

12

Rib-shaped strip

13

groove

14

Stege

Claims (11)

Container ( 1 ) made of thermoplastic material with at least one inner reinforcing rib ( 3 ) in a container wall ( 2 ), wherein the reinforcing rib ( 3 ) by at least one line-shaped groove track ( 4 ) in a container outer wall ( 2a ), the groove track ( 4 ) over a length on the container outer wall ( 2a ), the groove track through a plurality of depressions ( 5 ) in the container outer wall ( 2a ) is formed, which are arranged at a distance from each other and wherein between the wells ( 5 ) each material bridges ( 6 ) are provided, each having a smaller depth than the recesses ( 5 ). Container according to claim 1, characterized in that the plastic of the container wall ( 2 ) in the area of material bridges ( 6 ) is accumulated, so that the wall thickness of the container wall ( 2 ) in the area of material bridges ( 6 ) is larger than in the area of the depressions ( 5 ). Container according to one of claims 1 or 2, characterized in that the wall thickness of the container wall ( 2 ) in the area of material bridges ( 6 ) is stronger than the wall thickness of the container wall ( 2 ) outside the groove track ( 4 ). Container according to one of claims 1 to 3, characterized in that the depressions ( 5 ) have a length and a width and that the length is about 1 to 6 times, preferably the 3 times the width of the wells is. Container according to claim 4, characterized in that the material bridges ( 6 ) have a length which is 0.3 times to 0.5 times the length of the depressions ( 5 ) is. Container according to one of claims 1 to 5, characterized in that the depressions ( 5 ) are arranged at regular equal distances from each other. Container according to one of claims 1 to 6, characterized in that the material bridges ( 6 ) have a length which is less than or equal to twice the wall thickness of the container ( 1 ) outside the groove track ( 4 ). Container according to one of claims 1 to 7, characterized in that in the container wall ( 2 ) a plurality of reinforcing ribs ( 3 ), preferably in the form of a plurality of rectilinearly extending groove tracks ( 4 ), which preferably intersect or intersect. Method for producing a container ( 1 ) having the features of one of claims 1 to 8, characterized in that the container ( 1 ) is obtained by extrusion blow molding of at least one preform made of thermoplastic material or by deep drawing of a semi-finished product made of thermoplastic material, the method comprising the provision of the preform ( 9 ), the introduction of the plasticized preform ( 9 ) into a mold and the forming and shaping of the preform ( 9 ) within the tool, wherein at least one reinforcing rib ( 3 ) in the form of a line-shaped groove track ( 4 ) in the formation of the container ( 1 ) is produced within the tool by means of at least one tool insert or a tool slide, which serves as a rib-shaped strip ( 12 ) formed in a cavity ( 11 ) of the tool protrudes, wherein the bar ( 12 ) a plurality of grooves ( 13 ) and bridges ( 14 ) and wherein the webs ( 14 ) Wells ( 5 ) in the container outer wall ( 2a ) and in the grooves ( 13 ) plasticized plastic is accumulated. Method according to claim 9, characterized in that the grooves ( 13 ) have a length and a width and a depth that the length of the grooves ( 13 ) the length of the material bridges ( 6 ) and that the length of the grooves ( 13 ) is dimensioned so that the wall thickness of the molded container ( 1 ) in the area of material bridges ( 6 ) greater than the wall thickness of the container ( 1 ) in the area of the depressions ( 5 ) is preferably larger than outside the groove track ( 4 ). Method according to claim 9 or 10, characterized in that the length of the grooves ( 13 ) between 0.5 times and 4 times the wall thickness of the preform ( 9 ) is.

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